Houston (CNN) - The family of George H.W. Bush expressed confidence Thursday that the former president will be released shortly from an intensive care unit at a Houston hospital, where he is being treated for an elevated fever.

Bush family spokesman Jim McGrath said Bush was moved into the ICU so hospital personnel could more easily keep tabs on his condition, and that his family members were fully confident in the medical staff treating him. But while Bush's family hopes he is able to leave the hospital soon, they and Bush's doctors are in no hurry to rush him out, according to McGrath.Follow @politicalticker

The former president's most recent illness does not relate to his diagnosed Parkinsonism, McGrath said. On Wednesday, McGrath said Bush was in guarded condition and on a liquid diet. He added Thursday that the 41st president was being treated with Tylenol, among other things, but was in good spirits.

Doctors were initially treating Bush for bronchitis and a lingering cough. More recently he had been undergoing physical therapy in preparation for returning home, but developed a fever last week and began experiencing other complications that McGrath described as "a series of setbacks."

Bush was visited on Christmas Day by family members including his wife, Barbara, son Neil, daughter-in-law Maria and grandson Pierce. His daughter Doro visited Wednesday, and his son, former President George W. Bush, was making arrangements to visit as of Thursday. At 88, Bush is the oldest living former president, edging out Jimmy Carter by about four months.

Jean Becker, Bush's chief of staff, sent supporters a note on Thursday with reassurances that the former president's condition is not dire.

"Is he sick? Yes. Does he plan on going anywhere soon? No. He has every intention of staying put," Becker wrote. "He would ask me to tell you to please put the harps back in the closet."

Bush's health care in Houston is "unequaled anywhere" she wrote, asking supporters to "keep him and the family in your prayers.

"I am thinking heaven has not seen such a barrage of prayer intentions since 'It's a Wonderful Life,'" she wrote, referring to the classic holiday movie.

McGrath, the spokesman, told CNN on Wednesday morning that Bush's "mood is relentlessly positive and includes humorous banter with his doctor."

Bush was first hospitalized from November 7 to 19, and then was readmitted to Houston Methodist Hospital on November 23. Bush and his wife live part of the year in Houston and spend summers at their compound in Kennebunkport, Maine.

In mid-December, his doctors expressed optimism he would be home for Christmas, but the fever and other complications have interfered with those plans.